The present application relates to an input device and an electronic apparatus using the same. It particularly relates to an input device which is applicable to an electronic apparatus such as a mobile phone and a camera.
Recently, a user has captured various kinds of contents to the mobile phone and a portable terminal such as personal digital assistants (PDA) and utilized them. The PDA and the like are respectively provided with input device such as a key board, a rotary operation member, i.e., jog dial, and a touch panel.
In the input device using the touch panel, the user performs a desired operation on the portable terminal and the like by inputting any position information with his or her finger or a stylus touching a display screen thereof. The touch panel includes a capacitive touch panel and a resistive touch panel. The capacitive touch panel has been widely accepted as the input device because it has been capable of being low-profiled and also has been designed flexibly to allow a variety in a shape of the panel itself.
For example, Japanese Patent Application Publication No. 2005-284416 has disclosed a digital camera which is provided with a capacitive touch panel (sensor) for slide-inputting on an upper plate of the camera main body. The user can perform an operation such as zoom-in, zoom-out, reproduction/forward/rewind, focus adjustment and volume adjustment by sliding his or her finger to a desired direction with the finger touching the capacitive input sheet.
Here, the following will describe a principle of the capacitive input device. As shown in FIGS. 1A through 1C, if the user wants to operate a hemisphere key top 2 when his or her finger 3 approaches (or touches) the sensor (touch panel) 1 (see FIG. 1A), any capacitance occurs between the sensor 1 and the finger 3. This is because a human body has conductivity. The capacitance occurring between the sensor 1 and the finger 3 is given by the following equation (1).C=(ε*S)/D  (1)
where C indicates the capacitance; ε indicates a permittivity of each material; S indicates an area of the finger 3; and D indicates a distance between the sensor 1 and the finger 3. The capacitance C alters in inversely proportion to the distance D between the sensor (touch panel) 1 and the finger 3.
Such input device senses position information based on the capacitance occurring when the user's finger 3 touches the sensor 1 so that it can perform desired processing which the user indicates by his or her touching operation.